Procedure and apparatus for wrapping a fodder bale with plastic

ABSTRACT

The invention relates to a procedure for wrapping a straw fodder bale with plastic. In the wrapping operation, to wrap the corner between the envelope surface and the end surface of the bale, the axis of rotation of the plastic roll is turned from an upright position into a substantially horizontal position and the bale is rotated so that the plastic film being stretched on the bale from the plastic roll ( 16 ) is caused to bend over the corner of the bale partly onto the envelope surface and partly onto the end surface of the bale.

[0001] The present invention relates to a procedure as defined in thepreamble of claim 1 and to an apparatus as defined in the preamble ofclaim 4 for wrapping a green fodder bale with plastic.

[0002] In prior art, wrapping machines for wrapping a round bale areknown in which a plastic film is wound around a rotating bale so that,at the end of the wrapping operation, the bale has a plastic filmwrapped around it as tightly as possible, the wrapping completelyenclosing the bale. The equipment in prior-art solutions includespicking means for picking up a bale from the ground, a wrapping tablerotating the bale, a wrapping arm revolving around the bale and providedwith a roll of plastic film, a plastic film holder and a plastic filmcutter. A known solution is presented in Finnish patent no. 91123, whichcorresponds to European patent EP0499285.

[0003] In previously known solutions, the bale is rotated on a wrappingtable about its longitudinal axis in a substantially horizontal positionwhile the wrapping arm, provided with a plastic film roll with asubstantially upright axis of rotation, is revolved at the same timeabout the bale in a horizontal plane. The idea is to surround the balewith a plastic layer as impermeable as possible that will admit no airinto the bale. To achieve a sufficiently impermeable layer, at least afour-fold, preferably six-fold plastic layer is needed on the envelopesurface of the bale. In addition, the bale is wrapped with individuallayers overlapping each other. Due to this known wrapping method, theplastic layers are laid on the bale in the manner shown in FIG. 1. Anacceptable layer thickness on the envelope surface of the bale isachieved, but at the same time much too much plastic is accumulated onthe end surface of the bale. Especially the central part is covered withas many as 30-40 plastic layers. This means wasting large amounts ofexpensive plastic. This is one of the drawbacks of prior-art solutions.

[0004] Another drawback with known solutions is that there are generallystalks sticking out of the edges of the envelope surface so that theends of the stalks are pressed against the plastic. The drier the hay isallowed to become before being wrapped, the more damage will the stalkends inflict on the plastic during wrapping as they stretch the plasticin the stalk end area so that it becomes very thin or is even pierced.Therefore, the total thickness of the plastic layer is not sufficient.

[0005] Another disadvantage with prior-art solutions is that, as thevolume of the bale is diminished during storage because of fermentationstorage loss, the bale shrinks, with the result that the plastic filmwrapped longitudinally on the envelope surface becomes loose. The balevolume is reduced during storage by as much as 30% and the bale isdeformed at the same time. The plastic layer becoming thinner and looseleads to several problems. First, it permits the entry of air into thebale, increasing fermentation of the fodder and the risk of itscontracting mould. In addition, the stretched and slackened plastic onthe soft envelope surface of the bale is easily pierced by stubble andother sharp objects on the grassland.

[0006] The object of the present invention is to eliminate theabove-mentioned disadvantages and to achieve a reliable and easy-to-useprocedure and apparatus for wrapping a fodder bale with plastic. Theprocedure of the invention is characterized by what is presented in thecharacterization part of claim 1. The apparatus of the invention ischaracterized by what is presented in the characterization part of claim4. Other embodiments of the invention are characterized by what ispresented in the other claims.

[0007] The solution of the invention provides the advantage that, thanksto a new wrapping method, less plastic is used while at the same timeproducing a durable plastic layer around the bale. The reduction in theamount of plastic needed is about 30-40% as excessively thick plasticlayers at the ends of the bale are avoided. Another advantage is that,when the plastic film is passed over the corner of the envelope surfaceof the bale in the manner provided by the invention, stalk ends stickingout will not damage the plastic as in previously known methods but arereadily bent under the plastic without stretching it. As a result, thequality of the wrapping and therefore also the quality of the fodder areimproved, both because the plastic at the corners of the bale is moredurable and because drier bales can be wrapped, thanks to the improveddurability. A further advantage is that the new wrapping method producesa more compact surface layer of the bale envelope because the envelopeof the bale can be more effectively compressed with the plastic as theplastic film is wound in a different direction. Therefore, between theplastic film and the fodder there remains no air, which would impair thefodder quality as a result of a breathing and fermenting reaction. Afurther advantage is a hard envelope surface, which is made very compactand seamless by the laminating action of the wrapping table and rollers.Because the plastic is tightly stretched about the bale when theenvelope surface is being wrapped, the bale retains its shape and theplastic remains impermeable and tight around the bale throughout thestorage period even if the size of the bale is reduced. A bale with ahard envelope surface according to the invention can resist stubble andother sharp objects on the grassland much better during handling than abale with a soft envelope surface wrapped in the traditional manner. Anadditional advantage is that the distance between the plastic rolls anddifferent parts of the bale is hardly varied at all during the wrappingoperation, which means that only slight transverse stretching weakeningthe plastic occurs, especially at the envelope surface and corners ofthe bale. A further advantage worth mentioning is that the inventionallows stepless variation of the overlap of the plastic layers in therange of 0-100%.

[0008] To sum up the advantages of the solution of the invention, it canbe stated that, by producing a better wrapping result than previouslyknown solutions, the invention reduces the risk of mould while allowingfodder of a better quality to be produced at a lower cost and with areduced consumption of plastic.

[0009] In the following, the invention will be described in detail bythe aid of an embodiment example with reference to the attacheddrawings, wherein

[0010]FIG. 1 presents a known solution for wrapping a fodder bale withplastic as seen from the side of the bale,

[0011]FIG. 2 presents a lateral view of a wrapping apparatus performinga wrapping operation,

[0012]FIG. 3 illustrates a first step in a wrapping operation accordingto the invention, as a lateral view of a simplified apparatus providedwith a double wrapping arm,

[0013]FIG. 4 illustrates the transition over a corner in a wrappingoperation according to the invention, as seen from the end of the bale,and

[0014]FIG. 5 illustrates the transition over a corner in a wrappingoperation according to the invention, as seen from above the bale.

[0015] First, the apparatus of the invention will be described, makingit easier to understand the method. The solution of the invention can beused in many different wrapping applications. In this example, thesolution of the invention is described as used in a wrapping apparatusfor so-called round bales, moving on its own wheels and pulled by asuitable machine. The basic component of the frame of the apparatusconsists of a tow bar 2 with wheels 4 at its rear end. Extending betweenthe front end of the tow bar and the wheels is an upper support arm 5rising from the tow bar and forming a rearward curvature, with awrapping arm 15 pivotally connected to its rear end. The wrapping arm isbent downward so that it can revolve horizontally about the bale 1without hitting the upper support arm. The wrapping arm is revolved bymeans of a drive mechanism 33 and a transmission element 14. Mounted atthe lower end of the wrapping arm is a plastic film roll 16 containingplastic film to be stretched about the fodder bale. The frame of plasticroll is connected to the lower end of the wrapping arm by a point midwaybetween the ends of the axis of rotation of the plastic roll, so theaxis of rotation can be turned between a horizontal position and avertical position about a joint 18 at the lower end of the wrapping armby means of an actuator 17.

[0016] The rear part of the frame is provided with lugs 7 for a wrappingtable 3. The wrapping table may be immovable, but in this example it canbe tilted by a power means 41 into an inclined position to allow a baleto be picked up or removed. Pivoted by their ends on the side beams aretwo turning rollers 10 and 13, with at least one belt 11 stretchedaround them so as to form a concave pocket for the fodder bale 1.Turning roller 10 is a driving roller, receiving its energy from ahydraulic motor 26. The front edge of the table is additionally providedwith a guard 12 to prevent the bale from falling over the front edge ofthe table. For picking up a bale from the field, the wrapping tablecomprises two picking devices 6 pivotally mounted on its rear corners,the picking action of the devices being implemented using a power means9.

[0017] Mounted on each side at the front edge of the wrapping table isguide roller 19 freely rotatable about its longitudinal axis, thefunction of which is to press the plastic film being bent over thecorner of the bale tightly against the end surface of the bale. The axisof the guide roller is substantially parallel to the plane of the endsurface of the bale. In addition, placed on each side of the wrappingtable at its front edge is a freely rotatable pressure roller 20 mountedat an oblique position as seen from above the bale with respect to thehorizontal axis of rotation of the bale and thus also with respect toits end and envelope surfaces. The pressure roller 20 is spring-loaded,with a spring pressing the pressure roller against the edge between theenvelope surface and the end surface of the bale during the wrappingoperation. For the sake of clarity, the supporting structures of theguide and pressure rollers have been omitted from the drawings. Theadvantage achieved is a better wrapping result, because both the guideroller and the pressure roller guide the plastic film in an optimalmanner over the corner of the bale.

[0018] In the procedure of the invention, the bale is treated asfollows. The working cycle can be regarded as starting from thesituation presented in FIG. 2, where a bale 1 has been lifted onto thewrapping table 3 and the plastic roll 16 is in an upright position. In afirst step of the wrapping operation, at least one lap turn is woundaround the bale by revolving the upright plastic roll 16 by means of thewrapping arm 15 in a horizontal plane about the immobile bale. In thisway, besides covering the end surface, a good gripping surface isachieved for keeping the plastic film fast when the wrapping directionis changed. If it is desirable to have more plastic at the end surface,then it is possible to wrap two layers about the bale with a smallcoverage, with an overlap of e.g. about 20%. In this case, the bale hasto be rotated in the traditional manner during the wrapping operation.FIG. 3 illustrates the first step in the wrapping procedure.

[0019] After this, a second step in the wrapping procedure is started.The plastic roll 16 is placed at the edge of the bale and turnedsubstantially into a horizontal position so that part of the plasticroll extends outside the plane of the bale end. Seen from above, theplastic roll 16 is now at an angle of about 45° relative to the side andend of the bale, as shown in FIG. 5. This advantageous position of theplastic roll is achieved without using any extra auxiliary equipment,because the plastic roll is mounted on a wrapping arm 15 revolvinghorizontally about the bale and having its vertical axis of rotationsubstantially at the center of the bale as seen from above. When thewrapping arm is in this position relative to the bale, the plastic rollis automatically in the correct position. The turning operation can beperformed either smoothly starting before the above-mentioned locationor at once when the plastic roll is already at this location. Therotation of the bale about its horizontal axis is now started, whereuponthe plastic film is stretched over the corner of the bale so that aportion of the film is pressed against the end surface while anotherportion of it is pressed against the envelope surface of the bale. Therelationship between these portions is e.g. about half and half. Due tothe oblique position of the plastic roll, the plastic film is pressedtightly against the end surface of the bale. The guide roller 19 and thepressure roller 20 provide an additional effect pressing the plastictightly against the bale. After this, the plastic roll 16 is revolved bymeans of the wrapping arm substantially in a horizontal plane while theaxis of rotation of the plastic roll itself is also substantially in ahorizontal plane. At the same time, the bale is rotated about itshorizontal axis, with the result that the plastic film is evenlystretched over the entire envelope surface of the bale. The rotarymovements of the wrapping arm and the bale are so synchronized that adesired overlap on the envelope surface is achieved. A suitable overlapis an 80-% coverage, in which case the envelope surface can be coveredwith at least four layers of plastic in a single wrapping cycle. Whenthe plastic roll 16 reaches the other edge of the bale, it is againdriven somewhat past the end plane of the bale into an oblique positionwith respect to the bale in the same as at the first end, and theplastic film is allowed to be stretched over the corner of the bale bothonto the edge of the envelope surface and onto the end surface of thebale in the same way as at the first end. Stalk ends sticking out of theedge of the bale are now also bent under the plastic film. The guideroller 19 and the pressure roller 20 again provide an auxiliary effectguiding the plastic film about the corner.

[0020] After this, a third wrapping step is started. The plastic roll 16is again turned into an upright position either at once or slowly bysimultaneously turning the wrapping arm about the bale. In the latteralternative mode of operation, the plastic film settles better on thebale after the corner has been passed. Finally, the wrapping arm isagain revolved about the bale in the known manner through as manyrevolutions as necessary. At this phase, e.g. one layer with a coverageof 10-20% and in the same direction is needed, allowing the ends and therest of the bale to be well and coherently closed.

[0021] After the bale has been wrapped up, the pressing arm of a plasticcutter is raised up and the wrapping arm is driven into its position ofreadiness so that during the last revolution the plastic film goesaround the pressing arm of the plastic cutter. The pressing arm is againlowered, crimping the plastic in the direction of the plane of theplastic film, pressing it against a stop piece and severing the plasticfilm so that the plastic remains gripped between the stop piece and theplastic roll on the wrapping arm. After the plastic film has beensevered, the bale is free to be dropped off the wrapping table.

[0022] It is obvious to the person skilled in the art that the inventionis not limited to the example described above, but that it may be variedwithin the scope of the claims presented below. Thus, for example, thestructure of the apparatus may differ from that described above.Likewise, the wrapping operation can be controlled in different ways.The wrapping may be performed manually or it may be based on computercontrol or some other corresponding type of automatic control. E.g therotation of the bale in the second step of the wrapping procedure may bestarted by an automatic system simultaneously with the transition to thesecond step. Similarly, the control may be so implemented that the balewill rotate slowly starting from the first step, and after the plasticrolls have been turned into the horizontal position in the second step,the speed of rotation of the bale is increased, which, as the wrappingis performed in this direction, can be done without impairing thequality of the wrapping. The result is a considerable acceleration ofthe wrapping operation.

[0023] The operation of the apparatus may also be so constructed that,when the plastic roll 16 is at the corner of the bale, the plastic rollcan be driven back and forth in a horizontal plane near the corner ofthe bale for some time to allow a better lap-over of the plastic on theend and envelope of the bale. Similarly, by changing the relative speedsof the rotary motion of the bale and that of the wrapping arm, it ispossible to have the plastic film overlapped in different ways on thebale.

[0024] In addition, instead of a single plastic roll, the apparatus beprovided with two plastic rolls 16, each being mounted either at the endof a separate wrapping arm or at the ends of a common double wrappingarm. A double wrapping arm has a shape resembling an inverted letter U,an individual wrapping arm forming one half of it. In this case, theplastic rolls 16 are caused to start out simultaneously from oppositecorners of the bale and the movements of the plastic rolls aresynchronized with respect to each other. FIG. 3 illustrates a situationlike this. It shows a plastic film 22 at the left-hand rear corner ofthe bale as seen in the direction of observation of the figure, andcorrespondingly a plastic film 21 which has been stretched across thefront end of the bale and is now at the right-hand front corner, both ofwhich plastic films are now passing over the corner of the bale. Eachplastic roll is driven from one corner of the bale to the other, and theplastic film may be wound with half the amount of overlap compared withthe use of a single plastic roll. This produces a very good and fastwrapping result. Another way of controlling the wrapping operation is tostart driving the plastic rolls from the middle part of the bale with anormal overlap. In this case, the plastic rolls move toward oppositecorners of the bale, one in front of the bale and the other behind it.With each plastic roll, only one corner of the bale is now wrapped. Inthis case, too, the operation is very fast because the distance to becovered by each roll is shorter than in the case of a single plasticroll. For each plastic roll, separate guide and pressing devices 19 and20 are needed, placed symmetrically on opposite sides of the bale.

1. Procedure for wrapping a bale of hay or straw, such as a bale ofstraw fodder, with plastic, in which procedure the bale (1) of strawfodder to be wrapped is wrapped with several layers of plastic filmwound off from at least one plastic roll (16) provided in the wrappingapparatus, characterized in that in the wrapping operation, to wrap thecorner between the envelope surface and the end surface of the bale, theaxis of rotation of the plastic roll (16) is held in a substantiallyhorizontal position while the bale is rotated so that the plastic filmbeing stretched on the bale from the plastic roll (16) is caused to bendover the corner of the bale partly onto the envelope surface and partlyonto the end surface of the bale.
 2. Procedure as defined in claim 1 forwrapping a straw fodder bale with plastic, characterized in that, in afirst step in the wrapping operation, at least one lap turn of plasticfilm is wrapped about the bale by revolving a wrapping arm (15) aboutthe bale substantially in a horizontal plane while the axis of rotationof the plastic roll (16) is in a substantially upright position, andthat, in a second step in the wrapping operation, with the axis ofrotation of the plastic roll (16) in a substantially horizontalposition, the bale is rotated about its horizontal axis and the plasticfilm is caused to be wound about the bale so that the film is firststretched over a first corner of the bale partly onto the end surfaceand partly onto the envelope surface of the bale, whereupon the entireenvelope surface of the bale is wrapped with plastic film by moving theplastic roll (16) in a substantially horizontal plane toward the secondend of the bale and winding the plastic film with a suitable overlap,and finally the plastic film is stretched over the second corner of thebale partly onto the envelope surface and partly onto the second endsurface, and that, in a third step in the wrapping operation, at leastone layer of plastic film is wrapped about the bale by revolving thewrapping arm (15) in a substantially horizontal plane while the axis ofrotation of the plastic roll (16) is in a substantially uprightposition.
 3. Procedure as defined in claim 1 or 2 for wrapping a strawfodder bale with plastic, characterized in that two plastic rolls (16)disposed on opposite sides of the bale are used, the first step in thewrapping operation consisting of wrapping at least one lap turn ofplastic film about the bale by revolving the plastic rolls (16) in asubstantially horizontal plane while the axis of rotation of the plasticrolls (16) is in a substantially upright position, and that, in a secondstep in the wrapping operation, with the axis of rotation of the plasticrolls (16) in a substantially horizontal position, the bale is rotatedabout its horizontal axis and the plastic film is caused to be so woundabout the bale that the film is first stretched over the corner of thebale closest to each roll partly onto the end surface and partly ontothe envelope surface of the bale, whereupon the entire envelope surfaceof the bale is wrapped with plastic film by moving the plastic rolls(16) in a substantially horizontal plane toward the bale end farthestaway from each plastic roll and winding the plastic film with a suitableoverlap, and finally the plastic film is stretched over the farthercorner of the bale partly onto the envelope surface and partly onto thesecond end surface, and that, in a third step in the wrapping operation,at least one layer of plastic film is wrapped about the bale byrevolving the wrapping arm (15) in a substantially horizontal planewhile the axis of rotation of the plastic rolls (16) is in asubstantially upright position.
 4. Procedure as defined in claim 1, 2 or3 for wrapping a straw fodder bale with plastic, characterized in that,when the plastic film is being wound over a corner of the bale, thehorizontal axis of rotation of the bale and the axis of rotation of theplastic roll are in a substantially horizontal position but in anoblique position relative to each other.
 5. Apparatus for wrapping abale of hay or straw, such as a straw fodder bale, with plastic, saidapparatus comprising at least a support (3) for the bale (1) to bewrapped, at least one plastic roll (16) and a controlling element (15)for stretching a plastic film wound off from the plastic layer about thebale, characterized in that the apparatus comprises at least acontrolling element (17) for changing the position of the axis ofrotation of the plastic roll (16) and guide and pressing devices (19,20) for guiding the plastic film as it is being moved over a corner. 6.Apparatus as defined in claim 5, characterized in that the guide roller(19) used as a guide device has been fitted to be pressed against theend surface of the bale and, correspondingly, the pressing roller (20)used as a pressing device has been fitted to be pressed against thecorner of the bale at an angle of about 45° with respect to the axis ofrotation of the bale.
 7. Apparatus as defined in claim 5, characterizedin that the apparatus is provided with a double wrapping arm with aplastic roll (16) at each end of it, and that the apparatus has twoguide rollers (19) functioning as guide devices, each being fitted to bepressed against one end surface of the bale, and similarly two pressingrollers (20) functioning as pressing devices, each being fitted to bepressed against a corner of the bale at an angle of about 45° withrespect to the axis of rotation of the bale.